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The Inadequacy of the TSH (Thyroid Stimulating Hormone) Test

What's Wrong with the Thyroid Stimulating Hormone (TSH) Test?

Many thyroid conditions have been and continue to be incorrectly diagnosed through exclusive use of TSH (Thyroid Stimulating Hormone) testing as the sole signifier of possible thyroid dysfunction. Unfortunately, TSH is wrongly considered by the majority of endocrinologists and many other physicians to be the only indicator required to produce an accurate and comprehensive analysis of one’s thyroid health. Because of this many people come away from their physicians as being misdiagnosed or having their thyroid condition completely disregarded.

Why TSH testing is not enough

Although it is an important factor in diagnosis, TSH testing alone is an inadequate measure of one’s overall thyroid health and activity. It is important to understand where TSH falls short in providing a comprehensive look at one’s well-being. TSH gives a marker for the levels of T3 within the pituitary itself but is inherently lacking in relaying information on the levels of T3 elsewhere in the body. TSH only measures how effectively the pituitary and thyroid gland communicate with each other. Although important, this does not provide information regarding hormone production and activity outside the pituitary.

A notable flaw with TSH this testing is that one’s TSH levels react differently than the rest of the body when the individual is experiencing physiologic stress. Such stress includes: depression, chronic fatigue, obesity, and premenstrual syndrome (PMS), just to name a few. If a person is suffering from one or more physiological or emotional stressors, levels found in the pituitary likely do not correlate with the rest of the body. Meaning that even though TSH may appear normal, that data is not reliably indicative of healthy global thyroid activity.

The validity of TSH testing also comes into question in regards to range standards. The widespread belief of many physicians is that normal TSH ranges between 0.5 to 4.5. However, this gap continues to grow because reference range is dependent on population averages in sample groups. In testing, the lab creates a statistical graph using the mean sample and adding two standard deviations. This creates a bell-shaped curve. Meaning that increased prevalence and extremity of thyroid conditions causes the range of “normal” TSH to become larger.

The condition of one’s thyroid is only considered abnormal if it lands within the top or bottom 2.5% of the test lab’s curve. Therefore, if we use the standard range of 0.5-4.5, if a patient’s results shifted from 4.0 to 1.0 it would not be considered abnormal even though that is a huge change. Unfortunately, many physicians rely exclusively on this standardized range and only take further action if the patient’s levels fall within the outermost percentages. Because of this, only extreme cases of hyperthyroidism and hypothyroidism are diagnosed.

In addition, TSH tests do not account for efficiency of dispersion of thyroid hormone throughout the body. Poor transport of thyroid hormones into cells can be a significant contributing factor in thyroid conditions. If TSH is the only test used in determining one’s thyroid health status, this important data remains undiscovered and very likely leads to incorrect diagnosis.

What more should be done?

Further testing is required in order to have a comprehensive understanding of one’s complete thyroid health. The complexity of the thyroid system requires assessment of other factors in addition to TSH. For an appropriately thorough examination tests should include Free T4, Free T3, Reverse T3, Free T3/Reverse T3 ratio, as well as Anti-Thyroid Peroxidase and Anti-Thyroglobulin.

Free T4 (Free Thyroxine)

Levels of Free T4 in the bloodstream signifies how much is available in reserve to be converted to T3 (the active hormone usable by cells). Standard ranges are cited as being between 0.8 to 2.8 ng/dl (nanograms per deciliter). That being said, most integrative physicians agree that patients with above median levels, resting above 1.3 or higher, tend to feel better than those whose levels fall below the median.

Free T3 (Free Triiodothyroxine)

As the most active thyroid hormone, it is important to gauge how much Free T3 is available for transport around the body. Examination of Free T3 provides a more comprehensive look at how much active thyroid hormone is available for the body’s thyroid receptors. Free T3 is more clinically relevant than measures of Total T3 in cases of hypothyroidism. Lab reference ranges can fall between 2.3 to 4.2 pg/mL (picogram per milliliter). However, like Free T4, integrative physicians recognize patients feel best when their levels reside in the top half, 3.2 or higher, and in numerous cases even 3.7 or higher.

Reverse T3

Reverse T3 is the biologically inactive form of T3 and highly elevated levels could point to improper conversion of T4 into T3. Without testing Reverse T3 levels a thyroid condition may not be diagnosed even with hypothyroid symptoms present. This is because Free T4, Free T3, and TSH are capable of maintaining standard ranges even if Reverse T3 is out of balance.

Free T3/Reverse T3 Ratio

The relationship between Reverse T3 and Free T3 is an important marker in understanding the degree of thyroid hormone transferred into cells. Reverse T3 acts as a break, slowing transfer of thyroid hormone. Whereas Free T3 attempts to put on the gas and deliver hormones. If there is overabundance of Reverse T3 this results in insufficient levels of thyroid hormone reaching the bloodstream and by extension the rest of the body. If the ratio between Reverse T3 and Free T3 falls outside appropriate levels, about 2(RT3) to 1(FT3), the bloodstream can receive too little or too much thyroid hormone.

Thyroid Antibodies

Gauging thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb) is necessary in attaining a comprehensive understanding of one’s thyroid health. Observation of these antibodies can lead to detection of significantly damaging autoimmune diseases. Diseases such as, Hashimoto’s thyroiditis, wherein one’s immune system attacks healthy thyroid tissue causing a thyroid hormone deficit that can lead to hypothyroidism, and Graves’ disease, which causes an overproduction of thyroid hormone (hyperthyroidism). Determining if a patient is afflicted with one of these conditions is done through testing of TPOAb and TgAb.

More Than TSH Testing Alone

By relying solely on TSH as a signifier of healthy thyroid activity an immense number of thyroid conditions are being overlooked and undiagnosed. Through comprehensive testing of all areas listed above in addition to TSH a more complete and accurate diagnosis can be attained. By utilizing and examining each possible contributor of thyroid dysfunction, rather than using TSH as a cover-all, physicians are better able to diagnose and assist those who are suffering from these conditions.